Submit/refresh issue in custom "Trip Calculator" page

Hello,

My client is a fishing tackle store that also offers inclusive fishing trips in Baja California. Their old site had a trip calculator that allowed users to input their desired trip information and get a price estimate. You can see the original page in action here: https://www.jigstop.com/trip-calculator.php

I am trying to get that page to work with Zen Cart. I have recreated the PHP and HTML to work with Zen by following this guide: http://www.zen-cart.com/wiki/index.php/Creating_new_pages
You can see my work in progress here: http://jigstop.com/tours/index.php?main_page=tripcalculator

Unfortunately, I'm having a couple of issues that I will address one at a time as they are solved:

1. When the user selects a Month, Day, etc, it refreshes as it should but loses the inputted data.

I hate working with someone else's code. This guy was very messy with his PHP, and now I'm left with the mess... I would appreciate any and all attempts to help fix this page so I can move on with the project.